Bright silver based quaternary nanostructures

ABSTRACT

Disclosed are nanostructures comprising Ag, In, Ga, and S and a shell comprising Ag, Ga and S, wherein the nanostructures have a peak wavelength emission of 480-545 nm and wherein at least about 80% of the emission is band-edge emission. Also disclosed are methods of making the nanostructures.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to the field of nanotechnology. More particularly,the invention provides nanostructures with a core comprising Ag, In, Ga,and S (AIGS) and a shell comprising Ag, Ga and S (AGS), wherein thenanostructures have a peak emission wavelength (PWL) between 480-545 nm,and wherein at least about 80% of the emission is band-edge emission.The disclosure also provides methods of making the AIGS/AGS core-shellnanostructures.

Background Art

Nanostructures comprising group semiconductors are promising candidatesfor non-toxic fluorescent materials. Uematsu et al., NPG Asia Materials10:713-726 (2018) disclose AgInS₂/GaS_(x) core/shell nanostructureswhere x ranged from 0.8 to 1.5. These core/shell nanostructuresexhibited band-edge emission and broad, redshifted defect emission.Reduction in the defect emission was obtained by modifying the shellingprocedure by the use of 1,3-dimethylthiourea (as sulfur source) andGa(acac)₃ to generate GaS, and by the use of a temperature gradientreaction. However, the band-edge emission was redshifted and defectemission persisted.

Kameyama et al., ACS Appl. Mater. Interfaces 10:42844-42855 (2018)disclose Ag—In—Ga—S (AIGS) nanostructures with significant defectemission. The defect emission was reduced by application of a GaS shell.But defect emission remained at about 15% of the intensity of theband-edge emission and the photoluminescence quantum yield was low(<30%).

A need remains in the art for AIGS nanostructures with greatly high bandedge emission (BE), narrow full width at half maximum (FWHM), highquantum yield (QY), and reduced redshifting.

BRIEF SUMMARY OF THE INVENTION

The present invention provides nanostructures comprising a corecomprising Ag, In, Ga, and S (AIGS) and a shell comprising Ag, Ga and S(AGS), wherein the nanostructures have a peak emission wavelength (PWL)in the range of 480-545 nm and wherein at least about 80% of theemission is band-edge emission, and wherein the nanostructures exhibit aquantum yield (QY) of 80-99.9%.

In some embodiments, the nanostructures have an emission spectrum with aFWHM of less than 40 nm. In some embodiments, the nanostructures have anemission spectrum with a FWHM of 36-38 nm.

In some embodiments, the nanostructures have a QY of 82-96%. In someembodiments, the nanostructures have a QY in the inclusive range of85-95%. In some embodiments, the nanostructures have a QY of 86-94%.

In some embodiments, the nanostructures have an OD₄₅₀/mass(mL·mg⁻¹·cm⁻¹) greater than or equal to 0.8. In some embodiments, thenanostructures have an OD₄₅₀/mass (mL·mg⁻¹·cm⁻¹) in the inclusive range0.8-2.5. In some embodiments, the nanostructures have an OD₄₅₀/mass(mL·mg⁻¹·cm⁻¹)in the inclusive range 0.87-1.9.

In some embodiments, the average diameter of the nanostructures is lessthan 10 nm by TEM. In some embodiments, the average diameter is about 5nm.

In some embodiments, at least about 80% of the emission is band-edgeemission.

In some embodiments, at least about 90% of the emission is band-edgeemission.

In some embodiments, the nanostructures are quantum dots.

The invention also provides a nanostructure composition comprising:

-   -   (a) at least one population of the nanostructures described        herein; and    -   (b) at least one organic resin.

In some embodiments, the nanostructure composition comprises at leastone second population of nanostructures that have a PWL greater than 545nm.

Also provided is a method of preparing the nanostructure compositiondescribed herein, the method comprising:

-   -   (a) providing at least one population of nanostructures        described herein; and    -   (b) admixing at least one organic resin with the at least one        population of (a).

In some embodiments, at least about 80% of the emission is band-edgeemission. In some embodiments, at least about 90% of the emission isband-edge emission.

Also provided is a device comprising the composition described herein.

Also provided is a film comprising the composition described herein,wherein the nanostructures are embedded in a matrix that comprises thefilm.

Also provided is a nanostructure molded article comprising:

-   -   (a) a first conductive layer;    -   (b) a second conductive layer; and    -   (c) a nanostructure layer between the first conductive layer and        the second conductive layer, wherein the nanostructure layer        comprises the composition described herein.

Also provided method of making the core/shell nanostructures describedherein, comprising:

-   -   (a) preparing a mixture comprising Ag—In—Ga—S (AIGS) cores, a        sulfur source, and a ligand;    -   (b) adding the mixture obtained in (a) to a mixture of a gallium        carboxylate and a ligand at a temperature of 180-300° C.;    -   (c) holding the temperature in the range of 180-300° C. for        5-300 minutes; and    -   (d) isolating the nanostructures.

In some embodiments, the ligand in (a) and (b) is an alkyl amine. Insome embodiments, the alkyl amine is oleylamine.

In some embodiments, the sulfur source is derived from S₈.

In some embodiments, the temperature in (a) and (b) is about 270° C.

In some embodiments, the mixture in (b) further comprises a solvent. Insome embodiments, the solvent is octadecene, dibenzyl ether or squalane.

In some embodiments, the ratio of gallium carboxylate to AIGS cores is0.008-0.2 mmol of gallium carboxylate per mg AIGS.

In some embodiments, at least about 80% of the emission is band-edgeemission. In some embodiments, at least about 90% of the emission isband-edge emission.

Also provided is a method of making the nanostructures described herein,comprising:

-   -   (a) preparing a mixture comprising Ag—In—Ga—S (AIGS) cores and a        gallium halide in a solvent and holding the mixture for a time        sufficient to give AIGS nanostructures with a PWL of 480-545 nm        and wherein at least about 60% of the emission is band-edge        emission, and    -   (b) isolating the nanostructures.

In some embodiments, the gallium halide is gallium iodide.

In some embodiments, the solvent comprises trioctylphosphine. In someembodiments, the solvent comprises toluene.

In some embodiments, the time sufficient in (a) is from 0.1-200 hours.In some embodiments, the time sufficient is about 20 hours.

In some embodiments, the mixture is held at 20 to 100° C. In someembodiments, the mixture is held at about room temperature.

In some embodiments, the molar ratio of gallium halide to AIGS cores isfrom about 0.1 to about 30.

Also provided method of making the core/shell nanostructures describedherein, comprising:

-   -   (a) preparing a mixture comprising Ag—In—Ga—S (AIGS) cores, a        sulfur source, a ligand and a gallium halide at 180-300° C.;    -   (b) holding the temperature in the range of 180-300° C. for        5-300 minutes; and    -   (c) isolating the nanostructures.

In some embodiments, the ligand in (a) is an alkyl amine. In someembodiments, the alkyl amine is oleylamine.

In some embodiments, the sulfur source is derived from S₈.

In some embodiments, the temperature in (a) and (b) is about 240° C.

In some embodiments, the mixture in (b) further comprises a solvent. Insome embodiments, the solvent is octadecene, dibenzyl ether or squalane.

In some embodiments, the ratio of gallium halide to AIGS cores is0.008-0.2 mmol of gallium carboxylate per mg AIGS.

In some embodiments, at least about 80% of the emission is band-edgeemission. In some embodiments, at least about 90% of the emission isband-edge emission.

The invention also provides a method of making AIGS/AGS core-shellnanostructures that unexpectedly have very high band edge emission(>90%) and, at the same time, very high quantum yield (80-99%). Themethod comprises

-   -   (a) reacting Ga(acetylacetonate)₃, InCl₃, and a ligand        optionally in a solvent at a temperature sufficient to give an        In—Ga reagent, and    -   (b) reacting the In—Ga reagent with Ag₂S nanostructures at a        temperature sufficient to make AIGS nanostructures,    -   (c) reacting the AIGS nanostructures with an oxygen-free Ga salt        in a solvent containing a ligand at a temperature sufficient to        form AIGS/AGS core-shell nanostructures.

In some embodiments, the ligand is an alkyl amine. In some embodiments,the alkylamine ligand is oleylamine. In some embodiments, the ligandacts as solvent and a second solvent is not required. In someembodiments, the solvent is present in the reaction mixture. In someembodiments, the solvent is a high boiling solvent such as octadecene,squalane, dibenzyl ether, or xylene. In some embodiments, thetemperature sufficient in (a) is 100 to 280° C.; the temperaturesufficient in (b) is 150 to 260° C.; and the temperature sufficient in(c) is 170 to 280° C. In some embodiments, the temperature sufficient in(a) is about 210° C., the temperature sufficient in (b) is about 210°C., and the temperature sufficient in (c) is about 240° C.

In some embodiments, a ligand is bound to the core-shell nanostructures.In some embodiments, the ligand is a silane. In some embodiments, thesilane is an aminoalkyltrialkoxysilane or thioalkyltrialkoxysilane. Insome embodiments, the aminoalkyltrialkoxysilane is3-aminopropyl)triethoxysilane or 3-mercapopropyl)triethoxysilane.

Also provided are the core-shell nanostructures with a silane ligandadhered to a substrate. In some embodiments, the substrate is glass. Insome embodiments, the glass is part of a quantum dot color conversionfilm. In some embodiments, the quantum dot color converter comprises

-   -   a back plane;    -   a display panel disposed on the back plane; and    -   a quantum dot layer comprising the nanostructures, the quantum        dot layer diposed on the display panel.

In some embodiments, the quantum dot layer comprises a patterned quantumdot layer. In some embodiments, the back plane comprises an LED, an LCD,an OLED, or a microLED.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are graphs depicting the absorption spectrum (FIG. 1A)and photoluminescence spectrum (FIG. 1B) of Ag—In—Ga—S (AIGS) cores.

FIG. 2 is a transmission electron microscopy (TEM) image of AIGS cores.

FIG. 3 is a graph showing the photoluminescence spectra of starting AIGScores (-) and AIGS core/AGS (Ag—Ga—S) shell (AIGS/AGS) (-)nanostructures.

FIG. 4 is a transmission electron microscopy (TEM) image of AIGS/AGScore/shell nanostructures.

FIGS. 5A and 5B are photoluminescence spectra of AIGS cores before (FIG.5A) and after (FIG. 5B) surface treatment with GaI₃/trioctylphosphine(TOP). Band-edge emission for AIGS nanostructures before surfacetreatment varied from 513-548 nm with total quantum yield (QY)(band-edge+defect emission) ranging from 5-15%. After surface treatmentwith GaI₃/TOP, the band-edge emission contribution was significantlyenhanced while emission wavelengths were maintained and the FWHM wasimproved (37-38 nm).

FIGS. 6A and 6B are TEM images of AIGS/AGS core/shell nanostructuresprepared by shelling in oleylamine with an oxygen-containing Ga(III)oleate source (FIG. 6A) and with an oxygen-free Ga(III) chloride source(FIG. 6B). The TEM images show that the final shells are similar in sizeand have similar band edge to trap emission properties.

FIG. 7 is a line graph of AIGS/AGS core/shell nanostructures prepared byshelling in oleylamine with an oxygen-containing Ga(III) oleate sourceand an oxygen-free Ga(III) chloride source. The two nanostructures showa similar emission spectra.

DETAILED DESCRIPTION OF THE INVENTION Definitions

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention pertains. The following definitionssupplement those in the art and are directed to the current applicationand are not to be imputed to any related or unrelated case, e.g., to anycommonly owned patent or application. Although any methods and materialssimilar or equivalent to those described herein can be used in thepractice for testing of the present invention, the preferred materialsand methods are described herein. Accordingly, the terminology usedherein is for the purpose of describing particular embodiments only, andis not intended to be limiting.

As used in this specification and the appended claims, the singularforms “a,” “an” and “the” include plural referents unless the contextclearly dictates otherwise. Thus, for example, reference to “ananostructure” includes a plurality of such nanostructures, and thelike.

The term “about” as used herein indicates the value of a given quantityvaries by +/−10% of the value. For example, “about 100 nm” encompasses arange of sizes from 90 nm to 110 nm, inclusive.

A “nanostructure” is a structure having at least one region orcharacteristic dimension with a dimension of less than about 500 nm. Insome embodiments, the nanostructure has a dimension of less than about200 nm, less than about 100 nm, less than about 50 nm, less than about20 nm, or less than about 10 nm. Typically, the region or characteristicdimension will be along the smallest axis of the structure. Examples ofsuch structures include nanowires, nanorods, nanotubes, branchednanostructures, nanotetrapods, tripods, bipods, nanocrystals, nanodots,quantum dots, nanoparticles, and the like. Nanostructures can be, e.g.,substantially crystalline, substantially monocrystalline,polycrystalline, amorphous, or a combination thereof. In someembodiments, each of the three dimensions of the nanostructure has adimension of less than about 500 nm, less than about 200 nm, less thanabout 100 nm, less than about 50 nm, less than about 20 nm, or less thanabout 10 nm.

The term “heterostructure” when used with reference to nanostructuresrefers to nanostructures characterized by at least two different and/ordistinguishable material types. Typically, one region of thenanostructure comprises a first material type, while a second region ofthe nanostructure comprises a second material type. In certainembodiments, the nanostructure comprises a core of a first material andat least one shell of a second (or third etc.) material, where thedifferent material types are distributed radially about the long axis ofa nanowire, a long axis of an arm of a branched nanowire, or the centerof a nanocrystal, for example. A shell can but need not completely coverthe adjacent materials to be considered a shell or for the nanostructureto be considered a heterostructure; for example, a nanocrystalcharacterized by a core of one material covered with small islands of asecond material is a heterostructure. In other embodiments, thedifferent material types are distributed at different locations withinthe nanostructure; e.g., along the major (long) axis of a nanowire oralong a long axis of arm of a branched nanowire. Different regionswithin a heterostructure can comprise entirely different materials, orthe different regions can comprise a base material (e.g., silicon)having different dopants or different concentrations of the same dopant.

As used herein, the “diameter” of a nanostructure refers to the diameterof a cross-section normal to a first axis of the nanostructure, wherethe first axis has the greatest difference in length with respect to thesecond and third axes (the second and third axes are the two axes whoselengths most nearly equal each other). The first axis is not necessarilythe longest axis of the nanostructure; e.g., for a disk-shapednanostructure, the cross-section would be a substantially circularcross-section normal to the short longitudinal axis of the disk. Wherethe cross-section is not circular, the diameter is the average of themajor and minor axes of that cross-section. For an elongated or highaspect ratio nanostructure, such as a nanowire, the diameter is measuredacross a cross-section perpendicular to the longest axis of thenanowire. For a spherical nanostructure, the diameter is measured fromone side to the other through the center of the sphere.

The terms “crystalline” or “substantially crystalline,” when used withrespect to nanostructures, refer to the fact that the nanostructurestypically exhibit long-range ordering across one or more dimensions ofthe structure. It will be understood by one of skill in the art that theterm “long range ordering” will depend on the absolute size of thespecific nanostructures, as ordering for a single crystal cannot extendbeyond the boundaries of the crystal. In this case, “long-rangeordering” will mean substantial order across at least the majority ofthe dimension of the nanostructure. In some instances, a nanostructurecan bear an oxide or other coating, or can be comprised of a core and atleast one shell. In such instances it will be appreciated that theoxide, shell(s), or other coating can but need not exhibit such ordering(e.g. it can be amorphous, polycrystalline, or otherwise). In suchinstances, the phrase “crystalline,” “substantially crystalline,”“substantially monocrystalline,” or “monocrystalline” refers to thecentral core of the nanostructure (excluding the coating layers orshells). The terms “crystalline” or “substantially crystalline” as usedherein are intended to also encompass structures comprising variousdefects, stacking faults, atomic substitutions, and the like, as long asthe structure exhibits substantial long range ordering (e.g., order overat least about 80% of the length of at least one axis of thenanostructure or its core). In addition, it will be appreciated that theinterface between a core and the outside of a nanostructure or between acore and an adjacent shell or between a shell and a second adjacentshell may contain non-crystalline regions and may even be amorphous.This does not prevent the nanostructure from being crystalline orsubstantially crystalline as defined herein.

The term “monocrystalline” when used with respect to a nanostructureindicates that the nanostructure is substantially crystalline andcomprises substantially a single crystal. When used with respect to ananostructure heterostructure comprising a core and one or more shells,“monocrystalline” indicates that the core is substantially crystallineand comprises substantially a single crystal.

A “nanocrystal” is a nanostructure that is substantiallymonocrystalline. A nanocrystal thus has at least one region orcharacteristic dimension with a dimension of less than about 500 nm. Insome embodiments, the nanocrystal has a dimension of less than about 200nm, less than about 100 nm, less than about 50 nm, less than about 20nm, or less than about 10 nm. The term “nanocrystal” is intended toencompass substantially monocrystalline nanostructures comprisingvarious defects, stacking faults, atomic substitutions, and the like, aswell as substantially monocrystalline nanostructures without suchdefects, faults, or substitutions. In the case of nanocrystalheterostructures comprising a core and one or more shells, the core ofthe nanocrystal is typically substantially monocrystalline, but theshell(s) need not be. In some embodiments, each of the three dimensionsof the nanocrystal has a dimension of less than about 500 nm, less thanabout 200 nm, less than about 100 nm, less than about 50 nm, less thanabout 20 nm, or less than about 10 nm.

The term “quantum dot” (or “dot”) refers to a nanocrystal that exhibitsquantum confinement or exciton confinement. Quantum dots can besubstantially homogeneous in material properties, or in certainembodiments, can be heterogeneous, e.g., including a core and at leastone shell. The optical properties of quantum dots can be influenced bytheir particle size, chemical composition, and/or surface composition,and can be determined by suitable optical testing available in the art.The ability to tailor the nanocrystal size, e.g., in the range betweenabout 1 nm and about 15 nm, enables photoemission coverage in the entireoptical spectrum to offer great versatility in color rendering.

The term “oxygen-free ligand” refers to coordinating molecules that donot contain oxygen atoms that are able to coordinate to, or react with,metal ions used herein.

As used herein, the term “shell” refers to material deposited onto thecore or onto previously deposited shells of the same or differentcomposition and that result from a single act of deposition of the shellmaterial. The exact shell thickness depends on the material as well asthe precursor input and conversion and can be reported in nanometers ormonolayers. As used herein, “target shell thickness” refers to theintended shell thickness used for calculation of the required precursoramount. As used herein, “actual shell thickness” refers to the actuallydeposited amount of shell material after the synthesis and can bemeasured by methods known in the art. By way of example, actual shellthickness can be measured by comparing particle diameters determinedfrom transmission electron microscopy (TEM) images of nanocrystalsbefore and after a shell synthesis.

As used herein, the term “layer” refers to material deposited onto thecore or onto previously deposited layers and that result from a singleact of deposition of the core or shell material. The exact thickness ofa layer is dependent on the material.

A “ligand” is a molecule capable of interacting (whether weakly orstrongly) with one or more faces of a nanostructure, e.g., throughcovalent, ionic, van der Waals, or other molecular interactions with thesurface of the nanostructure.

“Photoluminescence quantum yield” (QY) is the ratio of photons emittedto photons absorbed, e.g., by a nanostructure or population ofnanostructures. As known in the art, quantum yield is typicallydetermined by the absolute change in photon counts upon illumination ofthe sample inside an integrating sphere, or a comparative method usingwell-characterized standard samples with known quantum yield values.

“Peak emission wavelength” (PWL) is the wavelength where the radiometricemission spectrum of the light source reaches its maximum.

As used herein, the term “full width at half-maximum” (FWHM) is ameasure of the size distribution of quantum dots. The emission spectraof quantum dots generally have the shape of a Gaussian curve. The widthof the Gaussian curve is defined as the FWHM and gives an idea of thesize distribution of the particles. A smaller FWHM corresponds to anarrower quantum dot nanocrystal size distribution. FWHM is alsodependent upon the emission wavelength maximum.

Band-edge emission is centered at higher energies (lower wavelengths)with a smaller offset from the absorption onset energy as compared tothe corresponding defect emission. Additionally, the band-edge emissionhas a narrower distribution of wavelengths compared to the defectemission. Both band-edge and defect emission follow normal(approximately Gaussian) wavelength distributions.

Optical density (OD) is a commonly used method to quantify theconcentration of solutes or nanoparticles. As per Beer-Lambert's law,the absorbance (also known as “extinction”) of a particular sample isproportional to the concentration of solutes that absorb a particularwavelength of light.

Optical density is the optical attenuation per centimeter of material asmeasured using a standard spectrometer, typically specified with a 1 cmpath length. Nanostructure solutions are often measured by their opticaldensity in place of mass or molar concentration because it is directlyproportional to concentration and it is a more convenient way to expressthe amount of optical absorption taking place in the nanostructuresolution at the wavelength of interest. A nanostructure solution thathas an OD of 100 is 100 times more concentrated (has 100 times moreparticles per mL) than a product that has an OD of 1.

Optical density can be measured at any wavelength of interest, such asat the wavelength chosen to excite a fluorescent nanostructure. Opticaldensity is a measure of the intensity that is lost when light passesthrough a nanostructure solution at a particular wavelength and iscalculated using the formula:OD=log₁₀*(I _(OUT) /I _(IN))where:

I_(OUT)=the intensity of radiation passing into the cell; and

I_(IN)=the intensity of radiation transmitted through the cell.

The optical density of a nanostructure solution can be measured using aUV-VIS spectrometer. Thus, through the use of a UV-VIS spectrometer itis possible to calculate the optical density to determine the amount ofquantum dots that are present in a sample.

Unless clearly indicated otherwise, ranges listed herein are inclusive.

A variety of additional terms are defined or otherwise characterizedherein.

AIGS Nanostructures

Provided are nanostructures comprising Ag, In, Ga, and S, wherein thenanostructures have a peak emission wavelength (PWL) between 480-545 nmand wherein at least about 60% of the emission is band-edge emission.

The percentage of band-edge emission is calculated by fitting theGaussian peaks (typically 2 or more) of the nanostructures emissionspectrum and comparing the area of the peak that is closer in energy tothe nanostructure bandgap (which represents the band-edge emission) tothe sum of all peak areas (band-edge+defect emission).

In one embodiment, the nanostructures have a FWHM emission spectrum ofless than 40 nm. In another embodiment, the nanostructures have a FWHMof 36-38 nm. In another embodiment, the nanostructures have a QY of atleast 58%. In another embodiment, the nanostructures have a QY of58-65%. In another embodiment, the nanostructures have a QY of about65%. In some embodiments, at least 80% of the emission is band-edgeemission. In other embodiments, at least 90% of the emission isband-edge emission. In other embodiments, at least 95% of the emissionis band-edge emission. In some embodiments, 92-98% of the emission isband-edge emission. In some embodiments, 93-96% of the emission isband-edge emission. In another embodiment, the nanostructures arequantum dots.

The AIGS nanostructures provide high blue light absorption. As apredictive value for blue light absorption efficiency, the opticaldensity at 450 nm on a per mass basis (OD₄₅₀/mass) is calculated bymeasuring the optical density of a nanostructure solution in a 1 cm pathlength cuvette and dividing by the dry mass per mL (mg/mL) of the samesolution after removing all volatiles under vacuum (<200 mTorr). In oneembodiment, the nanostructures provided herein have an OD₄₅₀/mass(mL·mg⁻¹·cm⁻¹) of at least 0.8. In another embodiment, thenanostructures have OD₄₅₀/mass (mL·mg⁻¹·cm⁻¹) of 0.8-2.5. In anotherembodiment, the nanostructures have an OD₄₅₀/mass (mL·mg⁻¹·cm⁻¹) of0.87-1.9.

In one embodiment, the nanostructures are core-shell nanostructures. Inanother embodiment, the nanostructures have Ag, In, Ga, and S in thecore and Ga and S in the shell (AIGS/GS). In another embodiment, thenanostructures have Ag, In, Ga, and S in the core and Ag, Ga and S inthe shell (AIGS/AGS)

In one embodiment, the average diameter of the nanostructures is lessthan 10 nm as measured by TEM. In another embodiment, the averagediameter is about 5 nm.

AIGS Nanostructures Prepared Using a GaX₃ (X=F, Cl, or Br) Precursor andan Oxygen-Free Ligand

Reports of AIGS preparation in the literature have not attempted toexclude oxygen-containing ligands. In the coating of AIGS with galliumcontaining shells, oxygen-containing ligands are often used to stabilizethe Ga precursor. Commonly gallium(III) acetylacetonate is used as aneasily air-handled precursor, whereas Ga(III) chloride requires carefulhandling due to moisture sensitivity. For example, in Kameyama et al.,ACS Appl. Mater. Interfaces 10:42844-42855 (2018), gallium (III)acetylacetonate was used as the precursor for core and core/shellstructures. Since gallium has a high affinity for oxygen,oxygen-containing ligands and using a gallium precursor that was notprepared under oxygen-free conditions may produce unwanted sidereactions, such as gallium oxides, when Ga and S precursors are used toproduce shells that contain a significant gallium content. These sidereactions may lead to defects in the shells and result in lower quantumyields.

In some embodiments, AIGS nanostructures are prepared using oxygen-freeGaX₃ (X=F, Cl, or Br) as a precursor in the preparation of the AIGScore. In some embodiments, AIGS nanostructures are prepared using GaX₃(X=F, Cl, or Br) as a precursor and an oxygen-free ligand in thepreparation of at least one shell on the AIGS nanostructure. In someembodiments, AIGS nanostructures are prepared using GaX₃ (X=F, Cl, orBr) as a precursor and an oxygen-free ligand in the preparation of theAIGS core and in the preparation of at least one shell on the AIGS core.In some embodiments, AIGS nanostructures are prepared using GaX₃ (X=F,Cl, or Br) as a precursor and an oxygen-free ligand in the preparationof the AIGS core and in the preparation of the shells on the AIGS core.

Provided are nanostructures comprising Ag, In, Ga, and S, wherein thenanostructures have a peak emission wavelength (PWL) between 480-545 nm,and wherein the nanostructures were prepared using a GaX₃ (X=F, Cl, orBr) precursor and an oxygen-free ligand.

In some embodiments, the nanostructures prepared using a GaX₃ (X=F, Cl,or Br) precursor and an oxygen-free ligand display a FWHM emissionspectrum of 35 nm or less. In some embodiments, the nanostructuresprepared using a GaX₃ (X=F, Cl, or Br) precursor and an oxygen-freeligand display a FWHM of 30-38 nm. In some embodiments, thenanostructures prepared using a GaX₃ (X=F, Cl, or Br) precursor and anoxygen-free ligand have a QY of at least 75%. In some embodiments, thenanostructures prepared using a GaX₃ (X=F, Cl, or Br) precursor and anoxygen-free ligand have a QY of 75-90%. In some embodiments, thenanostructures prepared using GaX₃ (X=F, Cl, or Br) precursor and anoxygen-free ligand have a QY of about 80%. In some embodiments, thenanostructures are quantum dots.

The AIGS nanostructures prepared herein provide high blue lightabsorption. In some embodiments, the nanostructures have an OD₄₅₀/mass(mL·mg⁻¹·cm⁻¹) of at least 0.8. In some embodiments, the nanostructureshave an OD₄₅₀/mass (mL·mg⁻¹·cm⁻¹) of 0.8-2.5. In another embodiment, thenanostructures have an OD₄₅₀/mass (mL·mg⁻¹·cm⁻¹) of 0.87-1.9.

In some embodiments, the nanostructures are core/shell nanostructures.In some embodiments, the nanostructures comprise Ag, In, Ga, and S inthe core and Ga and S in the shell. In some embodiments, thenanostructures are AIGS/AGS core/shell nanostructures are prepared usinga GaX₃ (X=F, Cl, or Br) precursor and an oxygen-free ligand in the core.In some embodiments, the nanostructures are AIGS/AGS core/shellnanostructures are prepared using a GaX₃ (X=F, Cl, or Br) precursor andan oxygen-free ligand in the shell. In some embodiments, thenanostructures are AIGS/AGS core/shell nanostructures are prepared usinga GaX₃ (X=F, Cl, or Br) precursor and an oxygen-free ligand in the coreand in the shell. In some embodiments, the AIGS/AGS core/shellnanostructures are prepared by reacting a pre-formed In—Ga reagent withAg₂S nanostructures to give AIGS nanostructures, followed by reactingwith an oxygen-free Ga salt to form the AIGS/AGS core-shellnanostructures.

Methods of Making AIGS Nanostructures

Provided are methods of making the core/shell nanostructures having aPWL of 480-545 nm, wherein at least about 60% of the emission isband-edge emission, comprising:

-   -   (a) preparing a mixture comprising Ag—In—Ga—S (AIGS) cores, a        sulfur source, and a ligand;    -   (b) adding the mixture obtained in (a) to a mixture of a gallium        carboxylate and a ligand at a temperature of 180-300° C. to give        nanostructures having a PWL of 480-545 nm, wherein at least        about 60% of the emission is band-edge emission; and    -   (c) isolating the nanostructures.

Also provided is method of making the AIGS/AGS core-shellnanostructures, comprising

reacting Ga(acetylacetonate)₃, InCl₃, and a ligand optionally in asolvent at a temperature sufficient to give an In—Ga reagent, and

reacting the In—Ga reagent with Ag₂S nanostructures at a temperaturesufficient to make AIGS nanostructures,

reacting the AIGS nanostructures with an oxygen-free Ga salt in asolvent containing a ligand at a temperature sufficient to form AIGS/AGScore-shell nanocrystals.

In some embodiments, the ligand is an alkyl amine. In some embodiments,the alkylamine ligand is oleylamine. In some embodiment, the ligand isused in excess and acts as a solvent and the recited solvent is absentin the reaction. In some embodiments, the solvent is present in thereaction. In some embodiment, the solvent is a high boiling solvent. Insome embodiments, the solvent is octadecene, squalane, dibenzyl ether orxylene. In some embodiments, the temperature sufficient in (a) is 100 to280° C.; the temperature sufficient in (b) is 150 to 260° C.; and thetemperature sufficient in (c) is 170 to 280° C. In some embodiments, thetemperature sufficient in (a) is about 210° C., the temperaturesufficient in (b) is about 210° C., and the temperature sufficient in(c) is about 240° C.

In some embodiments, at least 80% of the emission is band-edge emission.In other embodiments, at least 90% of the emission is band-edgeemission. In other embodiments, at least 95% of the emission isband-edge emission. In some embodiments, 92-98% of the emission isband-edge emission. In some embodiments, 93-96% of the emission isband-edge emission. In another embodiment, the nanostructures arequantum dots.

Examples of ligands are disclosed in U.S. Pat. Nos. 7,572,395,8,143,703, 8,425,803, 8,563,133, 8,916,064, 9,005,480, 9,139,770, and9,169,435, and in U.S. Patent Application Publication No. 2008/0118755.In one embodiment, the ligand is an alkyl amine. In some embodiments,the ligand is an alkyl amine selected from the group consisting ofdodecylamine, oleylamine, hexadecylamine, dioctylamine, andoctadecylamine.

In some embodiments, the sulfur source in (a) comprisestrioctylphosphine sulfide, elemental sulfur, octanethiol, dodecanethiol,octadecanethiol, tributylphosphine sulfide, cyclohexyl isothiocyanate,α-toluenethiol, ethylene trithiocarbonate, allyl mercaptan,bis(trimethylsilyl) sulfide, trioctylphosphine sulfide, or combinationsthereof. In some embodiments, the sulfur source in (a) is derived fromS₈.

In one embodiment, the sulfur source is derived from S₈.

In one embodiment, the temperature in (a) and (b) is about 270° C.

In some embodiments, the mixture in (b) further comprises a solvent. Insome embodiments, the solvent is trioctylphosphine, dibenzyl ether, orsqualane.

In some embodiments, the gallium carboxylate is a gallium C₂₋₂₄carboxylate. Examples of C₂₋₂₄ carboxylates include acetate, propionate,butanoate, pentanoate, hexanoate, heptanoate, octanoate, nonanoate,decanoate, undecanoate, tridecanoate, tetradecanoate, pentadecanoate,hexadecanoate, octadecanoate (oleate), nonadecanoate, and icosanoate. Inone embodiment, the gallium carboxylate is gallium oleate.

In some embodiments, the ratio of gallium carboxylate to AIGS cores is0.008-0.2 mmol gallium carboxylate per mg AIGS. In one embodiment, theratio of gallium carboxylate to AIGS cores is about 0.04 mmol galliumcarboxylate per mg AIGS.

In a further embodiment, the AIGS/AGS core/shell nanostructures areisolated, e.g., by precipitation. In some embodiments, the AIGS/AGScore/shell nanostructures are precipitated by addition of a non-solventfor the AIGS/AGS core/shell nanostructures. In some embodiments, thenon-solvent is a toluene/ethanol mixture. The precipitatednanostructures may be further isolated by centrifugation and washingwith a non-solvent for the nanostructures.

Also provided is a method of making the nanostructures having a PWL of480-545 nm, and wherein at least about 60% of the emission is band-edgeemission; comprising:

-   -   (a) preparing a mixture comprising AIGS cores and a gallium        halide in a solvent and holding the mixture for a time        sufficient to give AIGS nanostructures with a PWL of 480-545 nm,        wherein at least about 60% of the emission is band-edge        emission; and    -   (b) isolating the nanostructures.

In some embodiments, at least 80% of the emission is band-edge emission.In other embodiments, at least 90% of the emission is band-edgeemission. In other embodiments, at least 95% of the emission isband-edge emission. In another embodiment, the nanostructures arequantum dots.

In some embodiments, the gallium halide is gallium chloride, bromide oriodide. In one embodiment, the gallium halide is gallium iodide.

In some embodiments, the solvent comprises trioctylphosphine. In someembodiments, the solvent comprises toluene.

In some embodiments, the time sufficient in (a) is from 0.1-200 hours.In some embodiments, the time sufficient in (a) is about 20 hours.

In some embodiments, the mixture is held at 20 to 100° C. In oneembodiment, the mixture is held at about room temperature (20° C. to 25°C.).

In some embodiments, the molar ratio of gallium halide to AIGS cores isfrom about 0.1 to about 30.

In a further embodiment, the AIGS nanostructures are isolated, e.g., byprecipitation. In some embodiments, the AIGS nanostructures areprecipitated by addition of a non-solvent for the AIGS nanostructures.In some embodiments, the non-solvent is a toluene/ethanol mixture. Theprecipitated nanostructures may be further isolated by centrifugationand/or washing with a non-solvent for the nanostructures.

Methods of Making AIGS Nanostructures Prepared Using a GaX₃ (X=F, Cl, orBr) Precursor and an Oxygen-Free Ligand

Provided are methods of making the core/shell nanostructures having aPWL of 480-545 nm, wherein at least about 60% of the emission isband-edge emission, comprising:

-   -   (a) preparing a mixture comprising Ag—In—Ga—S (AIGS) cores, a        sulfur source, and a ligand;    -   (b) adding the mixture obtained in (a) to a mixture of a GaX₃        (X=F, Cl, or Br) and an oxygen-free ligand at a temperature of        180-300° C. to give nanostructures having a PWL of 480-545 nm,        wherein at least about 60% of the emission is band-edge        emission; and    -   (d) isolating the nanostructures.

In some embodiments, the preparing in (a) is under oxygen-freeconditions. In some embodiments, the preparing in (a) is in a glovebox.

In some embodiments, the adding in (b) is under oxygen-free conditions.In some embodiments, the adding in (b) is in a glovebox.

In some embodiments, at least 80% of the emission is band-edge emission.In other embodiments, at least 90% of the emission is band-edgeemission. In other embodiments, at least 95% of the emission isband-edge emission. In another embodiment, the nanostructures arequantum dots.

Examples of ligands are disclosed in U.S. Pat. Nos. 7,572,395,8,143,703, 8,425,803, 8,563,133, 8,916,064, 9,005,480, 9,139,770, and9,169,435, and in U.S. Patent Application Publication No. 2008/0118755.In some embodiments, the ligand in (a) is an oxygen-free ligand. In someembodiments, the ligand in (b) is an oxygen-free ligand. In someembodiments, the ligand in (a) and (b) is an alkyl amine. In someembodiments, the ligand is an alkyl amine selected from the groupconsisting of dodecylamine, oleylamine, hexadecylamine, dioctylamine,and octadecylamine. In some embodiments, the ligand in (a) isoleylamine. In some embodiments, the ligand in (b) is oleylamine. Insome embodiments, the ligand in (a) and (b) is oleylamine.

In one embodiment, the sulfur source is derived from S₈.

In one embodiment, the temperature in (a) and (b) is about 270° C.

In some embodiments, the mixture in (b) further comprises a solvent. Insome embodiments, the solvent is trioctylphosphine, dibenzyl ether, orsqualane.

In some embodiments, the GaX₃ is gallium chloride, gallium fluoride, orgallium iodide. In some embodiments, the GaX₃ is gallium chloride. Insome embodiments, the GaX₃ is Ga(III) chloride.

In some embodiments, the ratio of GaX₃ to AIGS cores is 0.008-0.2 mmolGaX₃ per mg AIGS. In some embodiments, the molar ratio of GaX₃ to AIGScores is from about 0.1 to about 30. In some embodiments, the ratio ofGaX₃ to AIGS cores is about 0.04 mmol GaX₃ per mg AIGS.

In some embodiments, the AIGS/AGS core/shell nanostructures areisolated, e.g., by precipitation. In some embodiments, the AIGS/AGScore/shell nanostructures are precipitated by addition of a non-solventfor the AIGS/AGS core/shell nanostructures. In some embodiments, thenon-solvent is a toluene/ethanol mixture. The precipitatednanostructures may be further isolated by centrifugation and/or washingwith a non-solvent for the nanostructures.

In some embodiments, the mixture in (a) is held at 20° C. to 100° C. Insome embodiments, the mixture in (a) is held at about room temperature(20° C. to 25° C.).

In some embodiments, the mixture in (b) is held at 200° C. to 300° C.for 0.1 hour to 200 hours. In some embodiments, the mixture in (b) isheld at 200° C. to 300° C. for about 20 hours.

AIGS Cores

The synthesis of Group III-V nanostructures has been described in U.S.Pat. Nos. 5,505,928, 6,306,736, 6,576,291, 6,788,453, 6,821,337,7,138,098, 7,557,028, 8,062,967, 7,645,397, and 8,282,412 and in U.S.Patent Appl. Publication No. 2015/236195. Synthesis of Group III-Vnanostructures has also been described in Wells, R. L., et al., “The useof tris(trimethylsilyl)arsine to prepare gallium arsenide and indiumarsenide,” Chem. Mater. 1:4-6 (1989) and in Guzelian, A. A., et al.,“Colloidal chemical synthesis and characterization of InAs nanocrystalquantum dots,” Appl. Phys. Lett. 69: 1432-1434 (1996).

In some embodiments, the core is doped. In some embodiments, the dopantof the nanocrystal core comprises a metal, including one or moretransition metals. In some embodiments, the dopant is a transition metalselected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W,Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, andcombinations thereof. In some embodiments, the dopant comprises anon-metal. In some embodiments, the dopant is ZnS, ZnSe, ZnTe, CdSe,CdS, CdTe, HgS, HgSe, HgTe, CuInS₂, CuInSe₂, AlN, AlP, AlAs, GaN, GaP,or GaAs.

In some embodiments, the core is purified before deposition of a shell.In some embodiments, the core is filtered to remove precipitate from thecore solution.

Nanostructure Shells

In some embodiments, the shell comprises a mixture of silver, galliumand sulfur elements that are deposited onto the core or a core/shell(s)structure.

In some embodiments, the shell is doped. In some embodiments, the dopantof the nanocrystal shell comprises a metal, including one or moretransition metals. In some embodiments, the dopant is a transition metalselected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W,Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, andcombinations thereof. In some embodiments, the dopant comprises anon-metal. In some embodiments, the dopant is ZnS, ZnSe, ZnTe, CdSe,CdS, CdTe, HgS, HgSe, HgTe, CuInS₂, CuInSe₂, AlN, AlP, AlAs, GaN, GaP,or GaAs.

In some embodiments, the core/shell nanostructure is purified beforedeposition of an additional shell. In some embodiments, the core/shellnanostructure is filtered to remove precipitate from the core/shellnanostructure solution.

Nanostructure Compositions

In some embodiments, the present disclosure provides a nanostructurecomposition comprising:

-   -   (a) at least one population of nanostructures, wherein the        nanostructures have a core that comprises Ag, In, Ga, and S        (AIGS), a shell that comprises Ag, Ga and S (AGS) have a PWL        between 480-545 nm, and wherein at least about 80% of the        emission is band-edge emission; and    -   (b) at least one organic resin.

In some embodiments, at least 80% of the emission is band-edge emission.In other embodiments, at least 90% of the emission is band-edgeemission. In other embodiments, at least 95% of the emission isband-edge emission. In some embodiments, 92-98% of the emission isband-edge emission. In some embodiments, 93-96% of the emission isband-edge emission. In another embodiment, the nanostructures arequantum dots.

In some embodiments, the nanostructure composition further comprises atleast one second population of nanostructures. The nanostructures havinga PWL between 480-545 nm emit green light. Additional populations ofnanostructures may be added that emit in the green, yellow, orange,and/or red regions of the spectrum. These nanostructures have a PWLgreater than 545 nm. In some embodiments, the nanostructures have a PWLbetween 550-750 nm. The size of the nanostructures determines theemission wavelength. The at least one second population ofnanostructures may comprise a Group III-V nanocrystal selected from thegroup consisting of BN, BP, BAs, BSb, AlN, AlP, AlAs, AlSb, GaN, GaP,GaAs, GaSb, InN, InP, InAs, and InSb. In some embodiments, the core ofthe second population of nanostructures is an InP nanocrystal.

Organic Resin

In some embodiments, the organic resin is a thermosetting resin or anultraviolet (UV) curable resin. In some embodiments, the organic resinis cured by a method that facilitates roll-to-roll processing.

Thermosetting resins require curing in which they undergo anirreversible molecular cross-linking process which renders the resininfusible. In some embodiments, the thermosetting resin is an epoxyresin, a phenolic resin, a vinyl resin, a melamine resin, a urea resin,an unsaturated polyester resin, a polyurethane resin, an allyl resin, anacrylic resin, a polyamide resin, a polyamide-imide resin, a phenolaminecondensation polymerization resin, a urea melamine condensationpolymerization resin, or combinations thereof.

In some embodiments, the thermosetting resin is an epoxy resin. Epoxyresins are easily cured without evolution of volatiles or by-products bya wide range of chemicals. Epoxy resins are also compatible with mostsubstrates and tend to wet surfaces easily. See Boyle, M. A., et al.,“Epoxy Resins,” Composites, Vol. 21, ASM Handbook, pages 78-89 (2001).

In some embodiments, the organic resin is a silicone thermosettingresin. In some embodiments, the silicone thermosetting resin is OE6630Aor OE6630B (Dow Corning Corporation, Auburn, Mich.).

In some embodiments, a thermal initiator is used. In some embodiments,the thermal initiator is AIBN [2,2′-Azobis(2-methylpropionitrile)] orbenzoyl peroxide.

UV curable resins are polymers that cure and quickly harden when exposedto a specific light wavelength. In some embodiments, the UV curableresin is a resin having as a functional group a radical-polymerizationgroup such as a (meth)acrylyloxy group, a vinyloxy group, a styrylgroup, or a vinyl group; a cation-polymerizable group such as an epoxygroup, a thioepoxy group, a vinyloxy group, or an oxetanyl group. Insome embodiments, the UV curable resin is a polyester resin, a polyetherresin, a (meth)acrylic resin, an epoxy resin, a urethane resin, an alkydresin, a spiroacetal resin, a polybutadiene resin, or a polythiolpolyeneresin.

In some embodiments, the UV curable resin is selected from the groupconsisting of urethane acrylate, allyloxylated cyclohexyl diacrylate,bis(acryloxy ethyl)hydroxyl isocyanurate, bis(acryloxyneopentylglycol)adipate, bisphenol A diacrylate, bisphenol Adimethacrylate, 1,4-butanediol diacrylate, 1,4-butanedioldimethacrylate, 1,3-butyleneglycol diacrylate, 1,3-butyleneglycoldimethacrylate, dicyclopentanyl diacrylate, diethyleneglycol diacrylate,diethyleneglycol dimethacrylate, dipentaerythritol hexaacrylate,dipentaerythritol monohydroxy pentaacrylate, di(trimethylolpropane)tetraacrylate, ethyleneglycol dimethacrylate, glycerol methacrylate,1,6-hexanediol diacrylate, neopentylglycol dimethacrylate,neopentylglycol hydroxypivalate diacrylate, pentaerythritol triacrylate,pentaerythritol tetraacrylate, phosphoric acid dimethacrylate,polyethyleneglycol diacrylate, polypropyleneglycol diacrylate,tetraethyleneglycol diacrylate, tetrabromobisphenol A diacrylate,triethyleneglycol divinylether, triglycerol diacrylate,trimethylolpropane triacrylate, tripropyleneglycol diacrylate,tris(acryloxyethyl)isocyanurate, phosphoric acid triacrylate, phosphoricacid diacrylate, acrylic acid propargyl ester, vinyl terminatedpolydimethylsiloxane, vinyl terminated diphenylsiloxane-dimethylsiloxane copolymer, vinyl terminatedpolyphenylmethylsiloxane, vinyl terminatedtrifluoromethylsiloxane-dimethylsiloxane copolymer, vinyl terminateddiethylsiloxane-dimethylsiloxane copolymer, vinylmethylsiloxane,monomethacryloyloxypropyl terminated polydimethyl siloxane, monovinylterminated polydimethyl siloxane, monoallyl-mono trimethylsiloxyterminated polyethylene oxide, and combinations thereof.

In some embodiments, the UV curable resin is a mercapto-functionalcompound that can be cross-linked with an isocyanate, an epoxy, or anunsaturated compound under UV curing conditions. In some embodiments,the polythiol is pentaerythritol tetra(3-mercapto-propionate) (PETMP);trimethylol-propane tri(3-mercapto-propionate) (TMPMP); glycoldi(3-mercapto-propionate) (GDMP);tris[25-(3-mercapto-propionyloxy)ethyl]isocyanurate (TEMPIC);di-pentaerythritol hexa(3-mercapto-propionate) (Di-PETMP); ethoxylatedtrimethylolpropane tri(3-mercapto-propionate) (ETTMP 1300 and ETTMP700); polycaprolactone tetra(3-mercapto-propionate) (PCL4MP 1350);pentaerythritol tetramercaptoacetate (PETMA); trimethylol-propanetrimercaptoacetate (TMPMA); or glycol dimercaptoacetate (GDMA). Thesecompounds are sold under the trade name THIOCURE® by Bruno Bock,Marschacht, Germany.

In some embodiments, the UV curable resin is a polythiol. In someembodiments, the UV curable resin is a polythiol selected from the groupconsisting of ethylene glycol bis (thioglycolate), ethylene glycolbis(3-mercaptopropionate), trimethylol propane tris (thioglycolate),trimethylol propane tris (3-mercaptopropionate), pentaerythritoltetrakis (thioglycolate), pentaerythritol tetrakis(3-mercaptopropionate)(PETMP), and combinations thereof. In some embodiments, the UV curableresin is PETMP.

In some embodiments, the UV curable resin is a thiol-ene formulationcomprising a polythiol and 1,3,5-Triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TTT). In some embodiments, the UV curable resin is athiol-ene formulation comprising PETMP and TTT.

In some embodiments, the UV curable resin further comprises aphotoinitiator. A photoinitiator initiates the crosslinking and/orcuring reaction of the photosensitive material during exposure to light.In some embodiments, the photoinitiator is acetophenone-based,benzoin-based, or thioxathenone-based.

In some embodiments, the photoinitiator is a vinyl acrylate-based resin.In some embodments, the photoinitiator is MINS-311RM (Minuta TechnologyCo., Ltd, Korea).

In some embodiments, the photoinitiator is IRGACURE® 127, IRGACURE® 184,IRGACURE® 184D, IRGACURE® 2022, IRGACURE® 2100, IRGACURE® 250, IRGACURE®270, IRGACURE® 2959, IRGACURE® 369, IRGACURE® 369 EG, IRGACURE® 379,IRGACURE® 500, IRGACURE® 651, IRGACURE® 754, IRGACURE® 784, IRGACURE®819, IRGACURE® 819Dw, IRGACURE® 907, IRGACURE® 907 FF, IRGACURE® Oxe01,IRGACURE® TPO-L, IRGACURE® 1173, IRGACURE® 1173D, IRGACURE® 4265,IRGACURE® BP, or IRGACURE® MBF (BASF Corporation, Wyandotte, Mich.). Insome embodiments, the photoinitiator is TPO(2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide) or MBF (methylbenzoylformate).

In some embodiments, the weight percentage of the at least one organicresin in the nanostructure composition is between about 5% and about99%, about 5% and about 95%, about 5% and about 90%, about 5% and about80%, about 5% and about 70%, about 5% and about 60%, about 5% and about50%, about 5% and about 40%, about 5% and about 30%, about 5% and about20%, about 5% and about 10%, about 10% and about 99%, about 10% andabout 95%, about 10% and about 90%, about 10% and about 80%, about 10%and about 70%, about 10% and about 60%, about 10% and about 50%, about10% and about 40%, about 10% and about 30%, about 10% and about 20%,about 20% and about 99%, about 20% and about 95%, about 20% and about90%, about 20% and about 80%, about 20% and about 70%, about 20% andabout 60%, about 20% and about 50%, about 20% and about 40%, about 20%and about 30%, about 30% and about 99%, about 30% and about 95%, about30% and about 90%, about 30% and about 80%, about 30% and about 70%,about 30% and about 60%, about 30% and about 50%, about 30% and about40%, about 40% and about 99%, about 40% and about 95%, about 40% andabout 90%, about 40% and about 80%, about 40% and about 70%, about 40%and about 60%, about 40% and about 50%, about 50% and about 99%, about50% and about 95%, about 50% and about 90%, about 50% and about 80%,about 50% and about 70%, about 50% and about 60%, about 60% and about99%, about 60% and about 95%, about 60% and about 90%, about 60% andabout 80%, about 60% and about 70%, about 70% and about 99%, about 70%and about 95%, about 70% and about 90%, about 70% and about 80%, about80% and about 99%, about 80% and about 95%, about 80% and about 90%,about 90% and about 99%, about 90% and about 95%, or about 95% and about99%.

Method of Preparing AIGS Nanostructure Composition

The present disclosure provides a method of preparing a nanostructurecomposition, the method comprising:

-   -   (a) providing at least one population of AIGS/AGS core-shell        nanostructures, the nanostructures comprising Ag, In, Ga, and S,        wherein the nanostructures have a PWL of between 480-545 nm, and        wherein at least about 80% of the emission is band-edge        emission; and    -   (b) admixing at least one organic resin with the composition of        (a).

In some embodiments, at least 80% of the emission is band-edge emission.In other embodiments, at least 90% of the emission is band-edgeemission. In other embodiments, at least 95% of the emission isband-edge emission. In some embodiments, 92-98% of the emission isband-edge emission. In some embodiments, 93-96% of the emission isband-edge emission. In another embodiment, the nanostructures arequantum dots.

The present disclosure also provides a method of preparing ananostructure composition, the method comprising:

-   -   (a) providing at least one population of nanostructures, the        nanostructures comprising Ag, In, Ga, and S, wherein the        nanostructures have a PWL of between 480-545 nm, wherein at        least about 60% of the emission is band-edge emission, and        wherein the nanostructures were prepared using a GaX₃ (X=F, Cl,        or Br) precursor and an oxygen-free ligand; and    -   (b) admixing at least one organic resin with the composition of        (a).

The present disclosure also provides a method of preparing ananostructure composition, the method comprising:

-   -   (a) providing at least one population of AIGS/AGS core-shell        nanostructures, wherein the nanostructures have a PWL of between        480-545 nm, wherein at least about 80% of the emission is        band-edge emission, and wherein the nanostructures exhibit a QY        of 80-99%; and    -   (b) admixing at least one organic resin with the composition of        (a).

In some embodiments, the at least one population of nanostructures isadmixed with at least one organic resin at an agitation rate of betweenabout 100 rpm and about 10,000 rpm, about 100 rpm and about 5,000 rpm,about 100 rpm and about 3,000 rpm, about 100 rpm and about 1,000 rpm,about 100 rpm and about 500 rpm, about 500 rpm and about 10,000 rpm,about 500 rpm and about 5,000 rpm, about 500 rpm and about 3,000 rpm,about 500 rpm and about 1,000 rpm, about 1,000 rpm and about 10,000 rpm,about 1,000 rpm and about 5,000 rpm, about 1,000 rpm and about 3,000rpm, about 3,000 rpm and about 10,000 rpm, about 3,000 rpm and about10,000 rpm, or about 5,000 rpm and about 10,000 rpm.

In some embodiments, the at least one population of nanostructures isadmixed with at least one organic resin for a time of between about 10minutes and about 24 hours, about 10 minutes and about 20 hours, about10 minutes and about 15 hours, about 10 minutes and about 10 hours,about 10 minutes and about 5 hours, about 10 minutes and about 1 hour,about 10 minutes and about 30 minutes, about 30 minutes and about 24hours, about 30 minutes and about 20 hours, about 30 minutes and about15 hours, about 30 minutes and about 10 hours, about 30 minutes andabout 5 hours, about 30 minutes and about 1 hour, about 1 hour and about24 hours, about 1 hour and about 20 hours, about 1 hour and about 15hours, about 1 hour and about 10 hours, about 1 hour and about 5 hours,about 5 hours and about 24 hours, about 5 hours and about 20 hours,about 5 hours and about 15 hours, about 5 hours and about 10 hours,about 10 hours and about 24 hours, about 10 hours and about 20 hours,about 10 hours and about 15 hours, about 15 hours and about 24 hours,about 15 hours and about 20 hours, or about 20 hours and about 24 hours.

In some embodiments, the at least one population of nanostructures isadmixed with at least one organic resin at a temperature between about−5° C. and about 100° C., about −5° C. and about 75° C., about −5° C.and about 50° C., about −5° C. and about 23° C., about 23° C. and about100° C., about 23° C. and about 75° C., about 23° C. and about 50° C.,about 50° C. and about 100° C., about 50° C. and about 75° C., or about75° C. and about 100° C. In some embodiments, the at least one organicresin is admixed with the at least one population of nanostructures at atemperature between about 23° C. and about 50° C.

In some embodiments, if more than one organic resin is used, the organicresins are added together and mixed. In some embodiments, a firstorganic resin is mixed with a second organic resin at an agitation rateof between about 100 rpm and about 10,000 rpm, about 100 rpm and about5,000 rpm, about 100 rpm and about 3,000 rpm, about 100 rpm and about1,000 rpm, about 100 rpm and about 500 rpm, about 500 rpm and about10,000 rpm, about 500 rpm and about 5,000 rpm, about 500 rpm and about3,000 rpm, about 500 rpm and about 1,000 rpm, about 1,000 rpm and about10,000 rpm, about 1,000 rpm and about 5,000 rpm, about 1,000 rpm andabout 3,000 rpm, about 3,000 rpm and about 10,000 rpm, about 3,000 rpmand about 10,000 rpm, or about 5,000 rpm and about 10,000 rpm.

In some embodiments, a first organic resin is mixed with a secondorganic resin for a time of between about 10 minutes and about 24 hours,about 10 minutes and about 20 hours, about 10 minutes and about 15hours, about 10 minutes and about 10 hours, about 10 minutes and about 5hours, about 10 minutes and about 1 hour, about 10 minutes and about 30minutes, about 30 minutes and about 24 hours, about 30 minutes and about20 hours, about 30 minutes and about 15 hours, about 30 minutes andabout 10 hours, about 30 minutes and about 5 hours, about 30 minutes andabout 1 hour, about 1 hour and about 24 hours, about 1 hour and about 20hours, about 1 hour and about 15 hours, about 1 hour and about 10 hours,about 1 hour and about 5 hours, about 5 hours and about 24 hours, about5 hours and about 20 hours, about 5 hours and about 15 hours, about 5hours and about 10 hours, about 10 hours and about 24 hours, about 10hours and about 20 hours, about 10 hours and about 15 hours, about 15hours and about 24 hours, about 15 hours and about 20 hours, or about 20hours and about 24 hours.

Properties of AIGS Nanostructures

In some embodiments, the nanostructure is a core/shell nanostructure. Insome embodiments, the nanostructure is an AIGS/AGS core-shellnanostructure

In some embodiments, the nanostructures display a high photoluminescencequantum yield. In some embodiments, the nanostructures display aphotoluminescence quantum yield of between about 50% and about 99%,about 50% and about 95%, about 50% and about 90%, about 50% and about85%, about 50% and about 80%, about 50% and about 70%, abot 50% andabout 60%, 60% and about 99%, about 60% and about 95%, about 60% andabout 90%, about 60% and about 85%, about 60% and about 80%, about 60%and about 70%, about 70% and about 99%, about 70% and about 95%, about70% and about 90%, about 70% and about 85%, about 70% and about 80%,about 80% and about 99%, about 80% and about 95%, about 80% and about90%, about 80% and about 85%, about 85% and about 99%, about 85% andabout 95%, about 80% and about 85%, about 85% and about 99%, about 85%and about 90%, about 90% and about 99%, about 90% and about 95%, orabout 95% and about 99%. In some embodiments, the nanostructures displaya photoluminescence quantum yield of between about 82% and about 96%,between about 85% and about 96%, and between about 93% and about 94%.

The photoluminescence spectrum of the nanostructures can coveressentially any desired portion of the spectrum. In some embodiments,the photoluminescence spectrum for the nanostructures have a emissionmaximum between 300 nm and 750 nm, 300 nm and 650 nm, 300 nm and 550 nm,300 nm and 450 nm, 450 nm and 750 nm, 450 nm and 650 nm, 450 nm and 550nm, 450 nm and 750 nm, 450 nm and 650 nm, 450 nm and 550 nm, 550 nm and750 nm, 550 nm and 650 nm, or 650 nm and 750 nm. In some embodiments,the photoluminescence spectrum for the nanostructures has an emissionmaximum of between 450 nm and 550 nm.

The size distribution of the nanostructures can be relatively narrow. Insome embodiments, the photoluminescence spectrum of the population ofnanostructures can have a full width at half maximum of between 10 nmand 60 nm, 10 nm and 40 nm, 10 nm and 30 nm, 10 nm and 20 nm, 20 nm and60 nm, 20 nm and 40 nm, 20 nm and 30 nm, 30 nm and 60 nm, 30 nm and 40nm, or 40 nm and 60 nm. In some embodiments, the photoluminescencespectrum of the population of nanostructures can have a full width athalf maximum of between 35 nm and 50 nm.

In some embodiments, the nanostructures emit light having a peakemission wavelength (PWL) between about 400 nm and about 650 nm, about400 nm and about 600 nm, about 400 nm and about 550 nm, about 400 nm andabout 500 nm, about 400 nm and about 450 nm, about 450 nm and about 650nm, about 450 nm and about 600 nm, about 450 nm and about 550 nm, about450 nm and about 500 nm, about 500 nm and about 650 nm, about 500 nm andabout 600 nm, about 500 nm and about 550 nm, about 550 nm and about 650nm, about 550 nm and about 600 nm, or about 600 nm and about 650 nm. Insome embodiments, the nanostructures emit light having a PWL betweenabout 500 nm and about 550 nm.

As a predictive value for blue light absorption efficiency, the opticaldensity at 450 nm on a per mass basis (OD₄₅₀/mass) can be calculated bymeasuring the optical density of a nanostructure solution in a 1 cm pathlength cuvette and dividing by the dry mass per mL of the same solutionafter removing all volatiles under vacuum (<200 mTorr) In someembodiments, the nanostructures have an optical density at 450 nm on aper mass basis (OD₄₅₀/mass) of between about 0.28/mg and about 0.5/mg,about 0.28/mg and about 0.4/mg, about 0.28/mg and about 0.35/mg, about0.28/mg and about 0.32/mg, about 0.32/mg and about 0.5/mg, about 0.32/mgand about 0.4/mg, about 0.32/mg and about 0.35/mg, about 0.35/mg andabout 0.5/mg, about 0.35/mg and about 0.4/mg, or about 0.4/mg and about0.5/mg.

Films

The nanostructures of the present invention can be embedded in apolymeric matrix using any suitable method. As used herein, the term“embedded” is used to indicate that the nanostructures are enclosed orencased with the polymer that makes up the majority of the component ofthe matrix. In some embodiments, the at least one nanostructurepopulation is suitably uniformly distributed throughout the matrix. Insome embodiments, the at least one nanostructure population isdistributed according to an application-specific distribution. In someembodiments, the nanostructures are mixed in a polymer and applied tothe surface of a substrate.

In some embodiments, the present disclosure provides a nanostructurefilm layer comprising:

-   -   (a) at least one population of nanostructures, the        nanostructures comprising AIGS/AGS core-shell nanostructures,        wherein the nanostructures have a PWL between 480 and 545,        wherein at least about 80% of the emission is band-edge        emission, and wherein the nanostructures exhibit a QY of        80-99.9%; and    -   (b) at least one organic resin.

The present disclosure also provides a method of preparing ananostructure film layer comprising:

-   -   (a) providing at least one population of AIGS/AGS core-shell        nanostructures, wherein the nanostructures have a PWL of between        480-545 nm, wherein at least about 80% of the emission is        band-edge emission, and wherein the nanostructures exhibit a QY        of 80-99.9%; and    -   (b) admixing at least one organic resin with the composition of        (a).

In some embodiments, at least 80% of the emission is band-edge emission.In other embodiments, at least 90% of the emission is band-edgeemission. In other embodiments, at least 95% of the emission isband-edge emission. In some embodiments, 92-98% of the emission isband-edge emission. In some embodiments, 93-96% of the emission isband-edge emission. In another embodiment, the nanostructures arequantum dots.

In some embodiments, the nanostructure film layer is a color conversionlayer.

The nanostructure composition can be deposited by any suitable methodknown in the art, including but not limited to painting, spray coating,solvent spraying, wet coating, adhesive coating, spin coating,tape-coating, roll coating, flow coating, inkjet vapor jetting, dropcasting, blade coating, mist deposition, or a combination thereof.Preferably, the quantum dot composition is cured after deposition.Suitable curing methods include photo-curing, such as UV curing, andthermal curing. Traditional laminate film processing methods,tape-coating methods, and/or roll-to-roll fabrication methods can beemployed in forming the quantum dot films of the present invention. Thequantum dot composition can be coated directly onto the desired layer ofa substrate. Alternatively, the quantum dot composition can be formedinto a solid layer as an independent element and subsequently applied tothe substrate. In some embodiments, the nanostructure composition can bedeposited on one or more barrier layers.

Spin Coating

In some embodiments, the nanostructure composition is deposited onto asubstrate using spin coating. In spin coating a small amount of materialis typically deposited onto the center of a substrate loaded a machinecalled the spinner which is secured by a vacuum. A high speed ofrotation is applied on the substrate through the spinner which causescentripetal force to spread the material from the center to the edge ofthe substrate. While most of the material would be spun off, a certainamount remains on the substrate, forming a thin film of material on thesurface as the rotation continues. The final thickness of the film isdetermined by the nature of the deposited material and the substrate inaddition to the parameters chosen for the spin process such as spinspeed, acceleration, and spin time. For typical films, a spin speed of1500 to 6000 rpm is used with a spin time of 10-60 seconds.

Mist Deposition

In some embodiments, the nanostructure composition is deposited onto asubstrate using mist deposition. Mist deposition takes place at roomtemperature and atmospheric pressure and allows precise control overfilm thickness by changing the process conditions. During mistdeposition, a liquid source material is turned into a very fine mist andcarried to the deposition chamber by nitrogen gas. The mist is thendrawn to the wafer surface by a high voltage potential between the fieldscreen and the wafer holder. Once the droplets coalesce on the wafersurface, the wafer is removed from the chamber and thermally cured toallow the solvent to evaporate. The liquid precursor is a mixture ofsolvent and material to be deposited. It is carried to the atomizer bypressurized nitrogen gas. Price, S. C., et al., “Formation of Ultra-ThinQuantum Dot Films by Mist Deposition,” ESC Transactions 11:89-94 (2007).

Spray Coating

In some embodiments, the nanostructure composition is deposited onto asubstrate using spray coating. The typical equipment for spray coatingcomprises a spray nozzle, an atomizer, a precursor solution, and acarrier gas. In the spray deposition process, a precursor solution ispulverized into micro sized drops by means of a carrier gas or byatomization (e.g., ultrasonic, air blast, or electrostatic). Thedroplets that come out of the atomizer are accelerated by the substratesurface through the nozzle by help of the carrier gas which iscontrolled and regulated as desired. Relative motion between the spraynozzle and the substrate is defined by design for the purpose of fullcoverage on the substrate.

In some embodiments, application of the nanostructure compositionfurther comprises a solvent. In some embodiments, the solvent forapplication of the quantum dot composition is water, organic solvents,inorganic solvents, halogenated organic solvents, or mixtures thereof.Illustrative solvents include, but are not limited to, water, D₂O,acetone, ethanol, dioxane, ethyl acetate, methyl ethyl ketone,isopropanol, anisole, γ-butyrolactone, dimethylformamide,N-methylpyrroldinone, dimethylacetamide, hexamethylphosphoramide,toluene, dimethylsulfoxide, cyclopentanone, tetramethylene sulfoxide,xylene, ε-caprolactone, tetrahydrofuran, tetrachloroethylene,chloroform, chlorobenzene, dichloromethane, 1,2-dichloroethane,1,1,2,2-tetrachloroethane, or mixtures thereof.

In some embodiments, the compositions are thermally cured to form thenanostructure layer. In some embodiments, the compositions are curedusing UV light. In some embodiments, the quantum dot composition iscoated directly onto a barrier layer of a quantum dot film, and anadditional barrier layer is subsequently deposited upon the quantum dotlayer to create the quantum dot film. A support substrate can beemployed beneath the barrier film for added strength, stability, andcoating uniformity, and to prevent material inconsistency, air bubbleformation, and wrinkling or folding of the barrier layer material orother materials. Additionally, one or more barrier layers are preferablydeposited over a quantum dot layer to seal the material between the topand bottom barrier layers. Suitably, the barrier layers can be depositedas a laminate film and optionally sealed or further processed, followedby incorporation of the nanostructure film into the particular lightingdevice. The nanostructure composition deposition process can includeadditional or varied components, as will be understood by persons ofordinary skill in the art. Such embodiments will allow for in-lineprocess adjustments of the nanostructure emission characteristics, suchas brightness and color (e.g., to adjust the quantum film white point),as well as the nanostructure film thickness and other characteristics.Additionally, these embodiments will allow for periodic testing of thequantum dot film characteristics during production, as well as anynecessary toggling to achieve precise nanostructure filmcharacteristics. Such testing and adjustments can also be accomplishedwithout changing the mechanical configuration of the processing line, asa computer program can be employed to electronically change therespective amounts of mixtures to be used in forming a nanostructurefilm.

Nanostructure Film Features and Embodiments

In some embodiments, the nanostructure films of the present inventionare used to form display devices. As used herein, a display devicerefers to any system with a lighting display. Such devices include, butare not limited to, devices encompassing a liquid crystal display (LCD),televisions, computers, mobile phones, smart phones, personal digitalassistants (PDAs), gaming devices, electronic reading devices, digitalcameras, and the like.

In some embodiments, the nanostructure films are part of a quantum dotcolor conversion layer.

In some embodiments, the display device comprises a quantum dot colorconverter. In some embodiments, the display device comprises a backplane; a display panel disposed on the back plane; and a quantum dotlayer comprising the nanostructure. In some embodiments, the quantum dotlayer is disposed on the display panel. In some embodiments, the quantumdot layer comprises a patterned quantum dot layer.

In some embodiments, the backplane comprises a blue LED, an LCD, anOLED, or a microLED.

In some embodiments, the display device comprises a quantum dot colorconverter. In some embodiments, the display device comprises a quantumdot layer comprising the nanostructure, and a light source elementselected from the group consisting of a blue LED, an OLED, a microLED,and a combination thereof. In some embodiments, the quantum dot layer isdisposed on the light source element. In some embodiments, the quantumdot layer comprises a patterned quantum dot layer. The patterned quantumdot layer may be prepared by any known method in the art. In oneembodiment, the patterned quantum dot layer is prepared by ink-jetprinting of a solution of the quantum dots. Suitable solvents for thesolution include, without limitation, dipropylene glycol monomethylether acetate (DPMA), polyglycidyl methacrylate (PGMA), diethyleneglycol monoethyl ether acetate (EDGAC), and propylene glycol methylether acetate (PGMEA). Volatile solvents may also be used in inkjetprinting because they allow for rapid drying. Volatile solvents includeethanol, methanol, 1-propanol, 2-propanol, acetone, methyl ethyl ketone,methyl isobutyl ketone, ethyl acetate, and tetrahydrofuran.

In some embodiments, the quantum dot layer has a thickness between about1 μm and about 25 μm. In some embodiments, the quantum dot layer has athickness between about 5 μm and about 25 μm. In some embodiments, thequantum dot layer has a thickness between about 10 μm and about 12 μm.

In some embodiments, the optical films containing nanostructurecompositions are substantially free of cadmium. As used herein, the term“substantially free of cadmium” is intended that the nanostructurecompositions contain less than 100 ppm by weight of cadmium. The RoHScompliance definition requires that there must be no more than 0.01%(100 ppm) by weight of cadmium in the raw homogeneous precursormaterials. The cadmium concentration can be measured by inductivelycoupled plasma mass spectroscopy (ICP-MS) analysis, and are on the partsper billion (ppb) level. In some embodiments, optical films that are“substantially free of cadmium” contain 10 to 90 ppm cadmium. In otherembodiment, optical films that are substantially free of cadmium containless than about 50 ppm, less than about 20 ppm, less than about 10 ppm,or less than about 1 ppm of cadmium.

Nanostructure Molded Article

In some embodiments, the present disclosure provides a nanostructuremolded article comprising:

-   -   (a) a first barrier layer;    -   (b) a second barrier layer; and    -   (c) a nanostructure layer between the first barrier layer and        the second barrier layer, wherein the nanostructure layer        comprises a population of nanostructures comprising AIGS/AGS        core-shell nanostructures, wherein the nanostructures have a PWL        between 480-545, wherein at least about 80% of the emission is        band-edge emission and exhibit a QY of 80-99.9%; and at least        one organic resin.

In some embodiments, the present disclosure provides a nanostructuremolded article comprising:

-   -   (a) a first barrier layer;    -   (b) a second barrier layer; and    -   (c) a nanostructure layer between the first barrier layer and        the second barrier layer, wherein the nanostructure layer        comprises a population of nanostructures comprising AIGS/AGS        core-shell nanostructures, wherein the nanostructures have a PWL        between 480-545, wherein at least about 80% of the emission is        band-edge emission and wherein the nanostructures exhibit a QY        of 80-99.9%; and at least one organic resin.

In some embodiments, at least 80% of the emission is band-edge emission.In other embodiments, at least 90% of the emission is band-edgeemission. In other embodiments, at least 95% of the emission isband-edge emission. In some embodiments, 92-98% of the emission isband-edge emission. In some embodiments, 93-96% of the emission isband-edge emission. In another embodiment, the nanostructures arequantum dots.

Barrier Layers

In some embodiments, the nanostructure molded article comprises one ormore barrier layers disposed on either one or both sides of thenanostructure layer. Suitable barrier layers protect the nanostructurelayer and the nanostructure molded article from environmental conditionssuch as high temperatures, oxygen, and moisture. Suitable barriermaterials include non-yellowing, transparent optical materials which arehydrophobic, chemically and mechanically compatible with thenanostructure molded article, exhibit photo- and chemical-stability, andcan withstand high temperatures. Preferably, the one or more barrierlayers are index-matched to the nanostructure molded article. Inpreferred embodiments, the matrix material of the nanostructure moldedarticle and the one or more adjacent barrier layers are index-matched tohave similar refractive indices, such that most of the lighttransmitting through the barrier layer toward the nanostructure moldedarticle is transmitted from the barrier layer into the nanostructurelayer. This index-matching reduces optical losses at the interfacebetween the barrier and matrix materials.

The barrier layers are suitably solid materials, and can be a curedliquid, gel, or polymer. The barrier layers can comprise flexible ornon-flexible materials, depending on the particular application. Barrierlayers are preferably planar layers, and can include any suitable shapeand surface area configuration, depending on the particular lightingapplication. In preferred embodiments, the one or more barrier layerswill be compatible with laminate film processing techniques, whereby thenanostructure layer is disposed on at least a first barrier layer, andat least a second barrier layer is disposed on the nanostructure layeron a side opposite the nanostructure layer to form the nanostructuremolded article according to one embodiment of the present invention.Suitable barrier materials include any suitable barrier materials knownin the art. For example, suitable barrier materials include glasses,polymers, and oxides. Suitable barrier layer materials include, but arenot limited to, polymers such as polyethylene terephthalate (PET);oxides such as silicon oxide, titanium oxide, or aluminum oxide (e.g.,SiO₂, Si₂O₃, TiO₂, or Al₂O₃); and suitable combinations thereof.Preferably, each barrier layer of the nanostructure molded articlecomprises at least 2 layers comprising different materials orcompositions, such that the multi-layered barrier eliminates or reducespinhole defect alignment in the barrier layer, providing an effectivebarrier to oxygen and moisture penetration into the nanostructure layer.The nanostructure layer can include any suitable material or combinationof materials and any suitable number of barrier layers on either or bothsides of the nanostructure layer. The materials, thickness, and numberof barrier layers will depend on the particular application, and willsuitably be chosen to maximize barrier protection and brightness of thenanostructure layer while minimizing thickness of the nanostructuremolded article. In preferred embodiments, each barrier layer comprises alaminate film, preferably a dual laminate film, wherein the thickness ofeach barrier layer is sufficiently thick to eliminate wrinkling inroll-to-roll or laminate manufacturing processes. The number orthickness of the barriers may further depend on legal toxicityguidelines in embodiments where the nanostructure s comprise heavymetals or other toxic materials, which guidelines may require more orthicker barrier layers. Additional considerations for the barriersinclude cost, availability, and mechanical strength.

In some embodiments, the nanostructure film comprises two or morebarrier layers adjacent each side of the nanostructure layer, forexample, two or three layers on each side or two barrier layers on eachside of the nanostructure layer. In some embodiments, each barrier layercomprises a thin glass sheet, e.g., glass sheets having a thickness ofabout 100 μm, 100 μm or less, or 50 μm or less.

Each barrier layer of the nanostructure film of the present inventioncan have any suitable thickness, which will depend on the particularrequirements and characteristics of the lighting device and application,as well as the individual film components such as the barrier layers andthe nanostructure layer, as will be understood by persons of ordinaryskill in the art. In some embodiments, each barrier layer can have athickness of 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less,20 μm or less, or 15 μm or less. In certain embodiments, the barrierlayer comprises an oxide coating, which can comprise materials such assilicon oxide, titanium oxide, and aluminum oxide (e.g., SiO₂, Si₂O₃,TiO₂, or Al₂O₃). The oxide coating can have a thickness of about 10 μmor less, 5 μm or less, 1 μm or less, or 100 nm or less. In certainembodiments, the barrier comprises a thin oxide coating with a thicknessof about 100 nm or less, 10 nm or less, 5 nm or less, or 3 nm or less.The top and/or bottom barrier can consist of the thin oxide coating, ormay comprise the thin oxide coating and one or more additional materiallayers.

Display Device with Nanostructure Color Conversion Layer

In some embodiments, the present invention provides a display devicecomprising:

-   -   (a) a display panel to emit a first light;    -   (b) a backlight unit configured to provide the first light to        the display panel; and    -   (c) a color filter comprising at least one pixel region        comprising a color conversion layer.

In some embodiments, the color filter comprises at least 1, 2, 3, 4, 5,6, 7, 8, 9, or 10 pixel regions. In some embodiments, when blue light isincident on the color filter, red light, white light, green light,and/or blue light may be respectively emitted through the pixel regions.In some embodiments, the color filter is described in U.S. Pat. No.9,971,076, which is incorporated herein by reference in its entirety.

In some embodiments, each pixel region includes a color conversionlayer. In some embodiments, a color conversion layer comprisesnanostructures described herein configured to convert incident lightinto light of a first color. In some embodiments, the color conversionlayer comprises nanostructures described herein configured to convertincident light into blue light.

In some embodiments, the display device comprises 1, 2, 3, 4, 5, 6, 7,8, 9, or 10 color conversion layers. In some embodiments, the displaydevice comprises 1 color conversion layer comprising the nanostructuresdescribed herein. In some embodiments, the display device comprises 2color conversion layers comprising the nanostructures described herein.In some embodiments, the display device comprises 3 color conversionlayers comprising the nanostructures described herein. In someembodiments, the display device comprises 4 color conversion layerscomprising the nanostructures described herein. In some embodiments, thedisplay device comprises at least one red color conversion layer, atleast one green color conversion layer, and at least one blue colorconversion layer.

In some embodiments, the color conversion layer has a thickness betweenabout 3 μm and about 10 μm, about 3 μm and about 8 μm, about 3 μm andabout 6 μm, about 6 μm and about 10 μm, about 6 μm and about 8 μm, orabout 8 μm and about 10 μm. In some embodiments, the color conversionlayer has a thickness between about 3 μm and about 10 μm.

The nanostructure color conversion layer can be deposited by anysuitable method known in the art, including but not limited to painting,spray coating, solvent spraying, wet coating, adhesive coating, spincoating, tape-coating, roll coating, flow coating, inkjet printing,photoresist patterning, drop casting, blade coating, mist deposition, ora combination thereof. In some embodiments, the nanostructure colorconversion layer is deposited by photoresist patterning. In someembodiments, nanostructure color conversion layer is deposited by inkjetprinting.

AIGS/AGS Core Shell Nanostructures with Silane Ligands

In some embodiments, the AIGS/AGS core-shell nanostructures furthercomprise a silane ligand. In some embodiments, the silane ligand is anaminoalkyltrialkoxysilane or mercaptoalkyltrialkoxysilane. Non-limitingexamples of aminoalkyltrialkoxysilanes include3-aminopropyl(trimethoxysilane), 3-aminopropyl(triethoxysilane),3-aminopropyl(diethoxymethoxysilane), 3-aminopropyl(tripropoxysilane),3-aminopropyl(dipropoxymethoxy silane),3-aminopropyl(tridodecanoxysilane),3-aminopropyl(tritetradecanoxysilane),3-aminopropyl(trihexadecanoxysilane),3-aminopropyl(trioctadecanoxysilane),3-aminopropyl(didodecanoxy)tetradecanoxysilane,3-aminopropyl(dodecanoxy)tetradecanoxy(hexadecanoxy)-silane,3-aminopropyl(dimethoxymethylsilane),3-aminopropyl(methoxydimethylsilane),3-aminopropyl(hydroxydimethylsilane),3-aminopropyl(diethoxymethylsilane),3-aminopropyl(ethoxydimethylsilane),3-aminopropyl(dipropoxymethylsilane),3-aminopropyl(propoxydimethylsilane),3-aminopropyl(diisopropoxymethylsilane),3-aminopropyl(isopropoxydimethylsilane),3-aminopropyl(dibutoxymethylsilane),3-aminopropyl(butoxydimethylsilane),3-aminopropyl(disiobutoxymethylsilane),3-aminopropyl(isobutoxydimethylsilane),3-aminopropyl(didodecanoxymethylsilane),3-aminopropyl(dodecanoxydimethylsilane),3-aminopropyl(ditetradecanoxymethylsilane),3-aminopropyl(tetradecanoxydimethylsilane),2-aminoethyl(trimethoxysilane), 2-aminoethyl(triethoxysilane),2-aminoethyl(diethoxymethoxysilane), 2-aminoethyl(tripropoxysilane),2-aminoethyl(dipropoxymethoxysilane), 2-aminoethyl(tridodecanoxysilane),2-aminoethyl(tritetradecanoxysilane),2-aminoethyl(trihexadecanoxysilane),2-aminoethyl(trioctadecanoxysilane),2-aminoethyl(didodecanoxy)tetradecanoxysilane,2-aminoethyl(dodecanoxy)tetradecanoxy(hexadecanoxy) silane,2-aminoethyl(dimethoxymethylsilane),2-aminoethyl(methoxydimethylsilane), 2-aminoethyl(diethoxymethylsilane),2-aminoethyl(ethoxydimethylsilane), 1-aminomethyl(trimethoxysilane),1-aminomethyl(triethoxysilane), 1-aminomethyl(diethoxymethoxy silane),1-aminomethyl(dipropoxymethoxysilane), 1-aminomethyl(tripropoxysilane),1-aminomethyl(trimethoxysilane), 1-aminomethyl(dimethoxymethylsilane),1-aminomethyl(methoxydimethylsilane),1-aminomethyl(diethoxymethylsilane),1-aminomethyl(ethoxydimethylsilane), 3-aminobutyl(trimethoxysilane),3-aminobutyl(triethoxysilane), 3-aminobutyl(diethoxymethoxysilane),3-aminobutyl(tripropoxysilane), 3-aminobutyl(dipropoxymethoxysilane),3-aminobutyl(dimethoxymethylsilane), 3-aminobutyl(diethoxymethylsilane),3-aminobutyl(dimethylmethoxysilane), 3-aminobutyl(dimethylethoxysilane),3-aminobutyl(tridodecanoxysilane), 3-aminobutyl(tritetradecanoxysilane),3-aminobutyl(trihexadecanoxysilane),3-aminobutyl(didodecanoxy)tetradecanoxysilane,3-aminobutyl(dodecanoxy)tetradecanoxy(hexadecanoxy) silane,3-amino-2-methylpropyl(trimethoxysilane),3-amino-2-methylpropyl(triethoxysilane),3-amino-2-methylpropyl(diethoxymethoxysilane),3-amino-2-methylpropyl(tripropoxysilane),3-amino-2-methylpropyl(dipropoxymethoxysilane),3-amino-2-methylpropyl(tridodecanoxysilane),3-amino-2-methylpropyl(tritetradecanoxysilane),3-amino-2-methylpropyl(trihexadecanoxysilane),3-amino-2-methylpropyl(trioctadecanoxysilane),3-amino-2-methylpropyl(didodecanoxy)tetradecanoxy-silane,3-amino-2-methylpropyl(dodecanoxy)tetradecanoxy-(hexadecanoxy)silane,3-amino-2-methylpropyl(dimethoxymethylsilane),3-amino-2-methylpropyl(methoxydimethylsilane),3-mercapto-2-methylpropyl(diethoxymethylsilane),3-mercapto-2-methylpropyl(ethoxydimethylsilane),3-mercapto-2-methylpropyl(dipropoxymethylsilane),3-amino-2-methylpropyl(propoxydimethylsilane),3-amino-2-methylpropyl(diisopropoxymethylsilane),3-amino-2-methylpropyl(isopropoxydimethylsilane),3-amino-2-methylpropyl(dibutoxymethylsilane),3-amino-2-methylpropyl(butoxydimethylsilane),3-amino-2-methylpropyl(disiobutoxymethylsilane),3-amino-2-methylpropyl(isobutoxydimethylsilane),3-amino-2-methylpropyl(didodecanoxymethylsilane),3-amino-2-methylpropyl(dodecanoxydimethylsilane),3-amino-2-methylpropyl(ditetradecanoxymethylsilane) and3-amino-2-methylpropyl(tetradecanoxydimethylsilane).

Non-limiting examples of mercaptoalkyltrialkoxysilanes include1-mercaptomethyltriethoxysilane, 1-mercaptoethyltrimethoxysilane,1-mercaptoethyltriethoxysilane, 2-mercaptoethyltrimethoxysilane,2-mercaptoethyltriethoxysilane, 3-mercapto-1-propyltrimethoxysilane,3-mercapto-1-propyltriethoxysilane, 3-mercapto-1-propylmethyldimethoxysilane, 3-mercapto-1-propylmethyldiethoxysilane,3-mercapto-1-propyldimethylethoxysilane, 3-mercapto- 1-propyldimethylmethoxysilane, 3-mercapto- 1 -propyltripropoxysilane,3-mercapto-1-propyltriisopropoxysilane,3-mercapto-1-propyltributoxysilane, 8-mercapto-1-octyltrimethoxysilane,8-mercapto-1-octyltriethoxysilane, 10-mercapto-1-decyltriethoxysilane,10-mercapto-1-decyltrimethoxysilane, mercaptomethyltriethoxysilane, andmercaptomethyltrimethoxysilane.

The AIGS/AGS core-shell nanostructures with an aminoalkyltrialkoxysilaneligand adhere much more strongly to glass compared to when apolyethylene glycol-containing ligand is used. Thus, AIGS/AGS- silaneligands are uniquely suitable for use in quantum dot color conversionlayers.

The following examples are illustrative and non-limiting, of theproducts and methods described herein. Suitable modifications andadaptations of the variety of conditions, formulations, and otherparameters normally encountered in the field and which are obvious tothose skilled in the art in view of this disclosure are within thespirit and scope of the invention.

EXAMPLES Example 1: AIGS Core Synthesis

Sample ID 1 was prepared using the following typical synthesis of AIGScores: 4 mL of 0.06 M CH₃CO₂Ag in oleylamine, 1 mL of 0.2 M InC13 inethanol, 1 mL of 0.95 M sulfur in oleylamine, and 0.5 mL dodecanethiolwere injected into a flask that contained 5 mL of degassed octadecene,300 mg of trioctylphosphine oxide, and 170 mg of galliumacetylacetonate. The mixture was heated to 40° C. for 5 minutes, thenthe temperature was raised to 210° C. and held for 100 minutes. Aftercooling to 180° C., 5 mL trioctylphosphine was added. The reactionmixture was transferred to a glovebox and diluted with 5 mL toluene. Thefinal AIGS product was precipitated by adding 75 mL ethanol,centrifuged, and redispersed in toluene. Sample IDs 2 and 3 were alsoprepared using this method. The optical properties of AIGS cores weremeasured as shown in FIGS. 1A and 1B and summarized in Table 1. AIGScore sizes and morphology were characterized by transmission electronmicroscopy (TEM) as shown in FIG. 2.

TABLE 1 Ag/(Ag + In/(In + Sample QY PWL FWHM In + Ga) Ga) ID (%) (nm)(nm) by ICP by ICP Note 1 44 519.5 47 0.39 0.44 50 mL flask scale 2 30514 50 0.37 0.41 10x scale up of Sample ID 1 3 40 518 52 0.38 0.45 10xscale up of Sample ID 1

Example 2: AIGS/AGS Core/Shell Synthesis

Sample ID 4 was prepared using the following typical synthesis of aAIGS/AGS core/shell: 2 mL of a 0.3 M gallium oleate solution inoctadecene and 12 mL oleylamine were introduced to a flask and degassed.The mixture was heated to 270° C. A pre-mixed solution of 1 mL of a 0.95M sulfur solution in oleylamine and 1 mL of isolated AIGS cores (15mg/mL) were co-injected. The shell growth was stopped after 30 minutes.The final core/shell product was transferred to a glovebox, washed withtoluene/ethanol, centrifuged, and redispersed in toluene. Sample IDs 4-8were also prepared using this method. The optical properties of AIGS/AGScore/shell materials are shown in FIG. 3 and summarized in Table 2.Growth of the shell resulted in nearly complete band-edge emission. Anincrease of the average particle size following shell growth wasobserved by TEM as shown in FIG. 4.

TABLE 2 Sample PWL FWHM OD₄₅₀ /mass ID (nm) (nm) QY (%) (mL · mg⁻¹ ·cm⁻¹) 4 516 38 61 — 5 517 36 58 0.87 6 520 37 53 1.04 7 514 38 64 0.72 8514 38 65 1.15

Example 3: Gallium Halide and Trioctylphosphine Surface Treatment

A roomtemperature surface modification of AIGS was conducted by theaddition of a GaI₃ solution in trioctylphosphine (0.01-0.25 M) to AIGSQDs and holding at room temperature for 20 hours. This treatment led toa significant enhancement of the band-edge emission as shown in FIGS. 5Aand 5B and summarized in Table 3, while maintaining substantially thepeak wavelength (PWL). Thus, the present invention solves the problem ofredshifting of the band-edge emission as observed with prior art methods(Uematsu et al., NPG Asia Materials 10:713-726 (2018); Kameyama et al.,ACS Appl. Mater. Interfaces 10:42844-42855 (2018)).

Compositional changes before and after GaI₃ addition were monitored byinductively coupled plasma atomic emission spectroscopy (ICP-AES) andenergy-dispersive X-ray spectroscopy (EDS) as summarized in Table 3.Composite images of In and Ga elemental distributions before and afterGaI₃/TOP surface treatment showed a radial distribution of In to Ga.

TABLE 3 PWL FWHM QY Band-edge Ag/(Ag + In + Ga) In/(In + Ga) Ag/(Ag +In + Ga) In/(In + Ga) ID (nm) (nm) (%) contribution by ICP by ICP by EDSby EDS 9 542 38 11 <45% 0.41 0.11 0.45 0.16 10 543 37 24 >80% 0.38 0.090.44 0.14

Example 4: AIGS/AGS Core/Shell Synthesis using Oxygen-Free Ga Sources

Sample ID 14 and 15 was prepared using the following typical synthesisof a AIGS/AGS core/shell using an oxygen-free Ga source: to 8 mLdegassed oleylamine, 400 mg of GaCl₃ dissolved in 400 μL toluene wasadded, followed by 40 mg of AIGS core and then 1.7 mL of 0.95 M sulfurin oleylamine. After heating to 240° C., the reaction was held for 2hours and then cooled. The final core/shell product was transferred to aglovebox, washed with toluene/ethanol, centrifuged, and dispersed intoluene. Sample IDs 15 and 16 were also prepared using this method.Sample IDs 11-13 were prepared using the method of Example 2. Theoptical properties of AIGS/AGS core/shell materials are shown in Table4.

TABLE 4 Sample PWL FWHM ID (nm) (nm) QY (%) BE % gallium source 11 52543 25 not Ga(III) deter- acetylacetonate) mined 12 516 34 73 90 galliumoleate 13 522 35 72 87 gallium oleate 14 521 35 85 86 Ga(III) chloride15 521 35 80 89 Ga(III) chloride 16 not not not not Ga(III) iodidedeter- deter- deter- deter- mined mined mined mined

As shown in Table 4, the quantum yield of AIGS/GS core/shell materialscan be improved by using Ga(III) chloride rather than Ga(III)acetylacetonate or gallium oleate when oleylamine is used as a solvent.FIGS. 6A and 6B compare the size of the final core/shell materials andindicate that core/shell materials prepared using Ga(III) chloride havesimilar size and similar band-edge to trap emission properties.Therefore, the increase in quantum yield (QY) is not simply due toincreasing the trap emission component. And, unexpectedly, it was foundthat when using Ga(III) iodide in place of Ga(III) chloride, the AIGScore appeared to dissolve in the reaction mixture and shelling did notoccur.

High-resolution TEM with energy-dispersive X-ray spectroscopy (EDS) ofSample 14 showed that the shell is better described as a gradient fromAIGS core to AGS shell which indicates that shelling under theseconditions results from a process in which Ag becomes incorporated intothe shell rather than growing a distinct thick layer of GS. This mayalso contribute to the improved quantum yield of the nanostructure dueto less strain from the shell.

Example 5: AIGS Core from Hot Injection of Pre-Formed Ag₂SNanostructures Mixed with Pre-Formed In—Ga Reagent

To make the Ag₂S nanostructures, under a N₂ atmosphere, 0.5 g of AgI and2 mL of oleylamine are added to 20 mL vial and stirred at 58° C. untilclear a solution is obtained. In a separate 20 mL vial, 5 mL DDT and 9mL of 0.95 M sulfur in oleylamine were mixed. The DDT+S-OYA mixture isadded to AgI solution and stirred for 10 min at 58° C. The obtained Ag₂Snanoparticle were used without wash.

To make the In—Ga reagent mixture, 1.2 g Ga(acetylacetonate)_(3, 0.35)gInCl₃, 2.5 mL oleylamine and 2.5 mL ODE charged to 100 mL flask. UnderN₂ atm heated to 210° C. and held for 10 min. Orange color and viscousproduct obtained.

To form AIGS nanoparticles, under N₂, 1.75 g of TOPO, 23 mL ofoleylamine and 25 mL ODE added to 250 mL flask. After degassing undervacuum, this solvent mixture is heated to 210° C. over 40 min. In a 40mL vial, the Ag₂S and the In—Ga reagent mixture from above are mixed at58° C. and transferred to syringe. The Ag—In—Ga mixture is then injectedto the solvent mixture at 210° C. and held 3 hr. After cooling to 180°C., 5 mL trioctylphosphine was added. The reaction mixture wastransferred to glovebox and diluted with 50 mL toluene. The finalproduct was precipitated by adding 150 mL ethanol, centrifuged, andredispersed in toluene. Such core were shelled by the method describedin Example 4. The optical properties of core/shell material made by thismethod at scales up to 24× that described above, are shown in Table 5.

TABLE 5 Sample PWL FWHM OD₄₅₀ /mass ID (nm) (nm) BE % QY (%) (mL · mg⁻¹· cm⁻¹) 17 510 34 96 86 — 18 524 38 93 94 1.1 19 520 38 93 88 1.3 20 51738 94 86 1.3 21 518 38 94 89 1.4 22 528 37 93 93 1.9

As shown in Table 5 the band edge emission percent and quantum yield areboth unexpectedly improved using the method of preforming some reactioncomponents of AIGS followed by injection into a hot solvent mixture.

Example 6—AIGS/AGS Nanostructures with a Silane Ligand

AIGS/GS core-shell nanostructures were reacted with a mixture ofJeffamine and (3-aminopropyl)trimethoxysilane (APTMS) to give a silaneligand complex. As shown in Table 6, the ligand-containing AIGS/AGSnanostructures maintained their QY of about 76%

TABLE 6 QD type QY AIGS/AGS 76.9% AIGS/AGS with Jeffamine/APTMS 76.3%

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. It will be apparent to persons skilled in the relevant artthat various changes in form and detail can be made therein withoutdeparting from the spirit and scope of the invention. Thus, the breadthand scope should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

All publications, patents and patent applications mentioned in thisspecification are indicative of the level of skill of those skilled inthe art to which this invention pertains, and are herein incorporated byreference to the same extent as if each individual publication, patentor patent application was specifically and individually indicated to beincorporated by reference.

What is claimed is:
 1. Nanostructures comprising Ag, In, Ga, and S(AIGS) and a shell comprising Ag, Ga and S (AGS), wherein thenanostructures have a peak emission wavelength (PWL) in the range of480-545 nm and wherein at least about 80% of the emission is band-edgeemission, and wherein the nanostructures exhibit a quantum yield (QY) of80-99.9%.
 2. The nanostructures of claim 1, wherein the nanostructureshave an emission spectrum with a FWHM of less than 40 nm.
 3. Thenanostructures of claim 2, wherein the nanostructures have an emissionspectrum with a FWHM of 36-38 nm.
 4. The nanostructures of claim 1,wherein the nanostructures have a QY of 82-96%.
 5. The nanostructures ofclaim 4, wherein the nanostructures have a QY of 85-95%.
 6. Thenanostructures of claim 4, wherein the nanostructures have a QY of86-94%.
 7. The nanostructures of claim 1, wherein the nanostructureshave an OD₄₅₀/mass (mL·mg⁻¹·cm⁻¹) greater than or equal to 0.8.
 8. Thenanostructures of claim 7, wherein the nanostructures have an OD₄₅₀/mass(mL·mg⁻¹·cm⁻¹) in the inclusive range 0.8-2.5.
 9. The nanostructures ofclaim 8, wherein the nanostructures have an OD₄₅₀/mass (mL·mg⁻¹·cm⁻¹) inthe inclusive range 0.87-1.9.
 10. The nanostructures of claim 1, whereinthe average diameter of the nanostructures is less than 10 nm by TEM.11. The nanostructures of claim 10, wherein the average diameter isabout 5 nm.
 12. The nanostructures of claim 1, wherein at least about80% of the emission is band-edge emission.
 13. The nanostructures ofclaim 1, wherein at least about 90% of the emission is band-edgeemission.
 14. The nanostructures of claim 13, wherein 92-98% of theemission is band-edge emission.
 15. The nanostructures of claim 13,wherein 93-96% of the emission is band-edge emission.
 16. Thenanostructures of claim 1, that are quantum dots.
 17. A nanostructurecomposition comprising: (a) at least one population of nanostructures ofclaim 1, and (b) at least one organic resin.
 18. The nanostructurecomposition of claim 17, further comprising at least one secondpopulation of nanostructures that have a PWL greater than 545 nm.
 19. Amethod of preparing a nanostructure composition, the method comprising:(a) providing at least one population of nanostructures of claim 1; and(b) admixing at least one organic resin with the at least one populationof (a).
 20. The method of claim 19, wherein 92-98% of the emission isband-edge emission.
 21. The method of claim 19, wherein 93-96% of theemission is band-edge emission.
 22. A device comprising the compositionof claim
 17. 23. A film comprising the composition of claim 17, whereinthe nanostructures are embedded in a matrix that comprises the film. 24.A nanostructure molded article comprising: (a) a first conductive layer;(b) a second conductive layer; and (c) a nanostructure layer between thefirst conductive layer and the second conductive layer, wherein thenanostructure layer comprises the composition of claim
 17. 25. A methodof making the nanostructures of claim 1, comprising (a) reactingGa(acetylacetonate)₃, InCl₃, and a ligand optionally in a solvent at atemperature sufficient to give an In-Ga reagent, and (b) reacting theIn-Ga reagent with Ag₂S nanostructures at a temperature sufficient tomake AIGS nanostructures, (c) reacting the AIGS nanostructures with anoxygen-free Ga salt in a solvent containing a ligand at a temperaturesufficient to form the nanostructures with a gradient comprising theAIGS core to AGS without a distinct layer of GS.
 26. The method of claim25, wherein the ligand is an alkylamine.
 27. The method of claim 26,wherein the alkylamine is oleylamine.
 28. The method of claim 25,wherein in (a) the solvent is present and is octadecene, squalane,dibenzylether or xylene.
 29. The method of claim 25, wherein thetemperature sufficient in (a) is 100 to 280° C.; the temperaturesufficient in (b) is 150 to 260° C.; and the temperature sufficient in(c) is 170 to 280° C.
 30. The method of claim 25, wherein thetemperature sufficient in (a) is about 210° C., the temperaturesufficient in (b) is about 210° C., and the temperature sufficient in(c) is about 240° C.